Orbital magnetism in CdOsO studied by X-ray magnetic circular dichroism

Matsuda, Yasuhiro*; Her, J.-L.*; Michimura, Shinji*; Inami, Toshiya; Suzuki, Motohiro*; Kawamura, Naomi*; Mizumaki, Masaichiro*; Kindo, Koichi*; Yamaura, Junichi*; Hiroi, Zenji*

X-ray magnetic circular dichroism (XMCD) at the -edge of Os has been investigated in the antiferromagneticphase of CdOsO, which exhibits a metal-insulator transition around 227 K. According to the sum rule, the XMCD spectra at 10 and 37 T clearly show that the ratio between the orbital magnetic moment () and spinmagnetic moment () is , and that and are coupled in parallel (). These phenomena are unusual in that the expected ground state of Os (5) is an orbital singlet in a cubic crystal field, and and should be antiparallel for a less than half-filled system in accordance with Hund's third rule. It is likely that the spin-orbit coupling is important for explaining the observed orbital magnetism.